1. Field of the Invention
The present invention relates to an image recording apparatus that irradiates a recording medium with light beams and forms an image on this recording medium, and an optical recording head used for this image recording apparatus.
2. Description of the Related Art
The following image recording apparatus is known: This image recording apparatus irradiates with laser beams a sheet-like recording medium with subliming dyestuff applied on a base film. This image recording apparatus selectively eliminates the subliming dyestuff by the thermal energy of these laser beams forming an image with the subliming dyestuff on the surface of the recording medium.
Such an image recording apparatus uses a drum winded with a recording medium, spins this drum to rotate the recording medium in the main scanning direction. While moving the laser head in the sub-scanning direction it irradiates this recording medium with laser beams. The laser beams irradiated are converged onto the surface of the recording medium by an optical lens.
To improve the processing speed by increasing the number of points recordable at a time, the laser head has an array of a plurality of optical fibers in the sub-scanning direction at regular intervals in a row. Thus, the resolution is determined by the distance between two neighboring optical fibers. To achieve recording with higher resolution, substrates that fix optical fibers may be tilted so as to substantially shorten the distance between two neighboring optical fibers in the sub-scanning direction.
By placing optical fibers in a row in the sub-scanning direction and increasing the number of optical fibers it is possible to increase the number of points recordable at a time improving the recording speed. However, the higher the number of optical fibers, the longer the optical fiber row becomes. When the length of an optical fiber row increases, the difference between the center and ends of the row in the distance between an optical fiber and the recording medium increases. This difference in the distance causes the laser beams to be out of focus deteriorating the picture quality. Furthermore, a longer optical fiber row requires not only an optical system lens of a greater diameter but also a greater laser head.
Furthermore, when tilting the substrates to obtain higher resolution, they must be tilted accurately, which would require the image recording apparatus to be provided with a controller for controlling the inclination of the substrates, which would mean additional costs.
Moreover, improving resolution requires the angle of tilting the substrates to be increased. However, a greater angle may cause the inconvenience of increasing the possibility of different laser beams overlapping one another.